POST /file/multipart/{uploadId}/presigned/url/batch

Get a batch of pre-signed URLS that should be used to upload file parts.
Each part will require a unique pre-signed URL. The client is expected to
PUT the contents of each part to the corresponding pre-signed URL. Each
per-signed URL will expire 15 minute after issued. If a URL has expired,
the client will need to request a new URL for that part.